Spring mechanism for power device

ABSTRACT

A spring mechanism for an electromagnetic drive unit converts or translates the movement and/or actuation of the electromagnet into a desired movement of the workpiece and enables simple and efficient tuning of the workpiece movement. The spring mechanism includes a housing, a spring connected to the housing, wherein at least two sections of the spring are movable with respect to the housing, a drive shaft that includes a first end having a magnet and a second end for attachment to a workpiece, and at least two tuning elements connecting the drive shaft to the movable portion of the spring. At least one of the tuning elements is adjustable. In one embodiment, the spring may be a flat spring, and the movable sections may each be positioned between a pair of cutouts defined in the spring.

BACKGROUND OF THE INVENTION

The present invention is directed to electromagnetically powereddevices, and, more particularly, to powered devices such as electrictoothbrushes having an electromagnetic drive unit.

One method for actuating the bristles, or other cleaning elements, of anelectric toothbrush or another device having a powered handle is anelectromagnetic drive positioned within the handle portion of thetoothbrush or other device. The electromagnet can be actuated by aswitch to alternate polarity at a desired frequency. A movable permanentmagnet (or a pair of permanent magnets) is positioned proximate to theelectromagnet, such that the permanent magnet is driven to oscillate atan oscillating frequency by the electromagnet when the electromagnet isactuated. A neck, which may or may not be elongated, including aworkpiece such as a brush head is typically attached to the permanentmagnet, such that the workpiece is driven to oscillate by the movementof the permanent magnet.

Recognizing the need to replace certain aspects of these workpieces,such as toothbrush bristles, after they are worn out or in order toprovide more options, e.g., to attach a different head with a differentfunction, manufacturers have designed replacement heads that fit ontoseparate electromagnetic drive units. The drive units may include thepower source, switch, fixed electromagnet, movable permanent magnet anddrive shaft, with the replacement heads including a neck and a workpiecesuch as a toothbrush head. In some instances, the replacement heads mayfurther include the permanent magnet, drive shaft and workpiece. Thereplacement heads can be removably attached to the drive units, forinstance, by threading or otherwise connecting a portion of thereplacement head onto a portion of the drive unit.

More recently, manufacturers have attempted to control the movement ofthese workpieces, in order to provide a more efficient and desirableworkpiece motion. For example, in the case of electric toothbrushes,manufacturers have attempted to control the movement of the cleaningelements in a rotational motion about the central longitudinal axis ofthe toothbrush. Difficulties arise in doing so, especially in the caseof toothbrushes with electromagnetic drives, because the generallylinear oscillation caused by the electromagnet must be converted intothe desired rotational motion. Some replacement heads include parts thatmay contribute to vibrations and/or noise in the electric toothbrushthat may be undesirable or annoying. In each situation, the motion ofthe workpiece can vary dramatically as the frequency of theelectromagnet approaches the resonant frequency of the drive shaft andworkpiece.

SUMMARY OF THE INVENTION

The present invention provides a spring mechanism for anelectromagnetically powered device that converts or translates themovement and/or actuation of the electromagnet into a desired movementof the workpiece and enables simple and efficient tuning of theworkpiece movement.

In one embodiment, the spring mechanism includes a housing, a springconnected to the housing, wherein at least a portion of the spring ismovable with respect to the housing, a drive shaft that includes a firstend having a magnet and a second end for attachment to a workpiece, andan adjustable tuning element connecting the drive shaft to the movableportion of the spring.

In one embodiment, the spring may be a flat spring, and the movableportion of the spring may be a spring section positioned between a pairof cutouts defined in the spring. The size and shape of the cutouts mayalso be varied in order to control the workpiece movement.

In one embodiment, the adjustable tuning element extends from the driveshaft to the movable portion of the spring, and is connected to thespring such that the adjustable tuning element places the movableportion of the spring under a degree of tension. The adjustable tuningelement may be threadedly connected between the drive shaft and themovable portion of the spring, such that the threaded connection enablesadjustment of the amount of the tension on the movable portion of thespring. More particularly, the tuning element may be a bolt extendingthrough the movable portion of the spring, through the drive shaft, andinto a nut on an opposite surface of the drive shaft.

The drive shaft may be rotatable about a pair of bearing surfacesdefining an axis of rotation extending along the bearing surfaces, andthe adjustable tuning element may be positioned between the bearingsurfaces. The bearing surfaces may be formed by a pair of rockersextending from the drive shaft.

In another embodiment, the spring mechanism may include two or more ofthe movable spring portions, and two or more adjustable tuning elements.For example, two of the movable spring portions may be aligned with oneanother along the longitudinal axis of the toothbrush. An adjustabletuning element may extend through each of the movable spring portions tothe drive shaft. In such an embodiment, the spring mechanism may notinclude bearing surfaces separate from the adjustable tuning elements,as the motion of the drive shaft may be controlled by the tuning of thetwo or more movable spring portions and adjustable tuning elements. Eachset of movable spring portions and adjustable tuning elements may beindividually tuned by adjusting the tension of the tuning element and/oradjusting the size and shape of the movable spring portion, in order toachieve the desired workpiece motion.

The spring mechanism may be implemented into a toothbrush drive unit orsome other personal care device drive unit, wherein the bristle head andneck are capable of being removed from the drive unit and replaced. Inanother embodiment, however, the spring mechanism may be incorporatedinto a replacement head for a toothbrush or for some other personal caredevice, wherein the bristle head and neck, drive shaft, and spring arereplaceable.

The present invention also provides a method for manufacturing a springmechanism for an electric toothbrush or other personal care device,including the steps of: providing a fixed housing defining a generallyhollow interior; providing a drive shaft extending at least in part intothe hollow interior of the fixed housing, the drive shaft having a firstend and a second end, the first end including a magnet and the secondend adapted to receive a workpiece; connecting a spring member to thefixed housing, the spring member having a movable section; connectingthe spring member to the drive shaft with an adjustable tuning member;and adjusting the tuning member to provide a desired degree of tensionon the movable section of the spring.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view according to one embodiment of the presentinvention showing a spring mechanism as disposed within a handle housingshown in broken lines, and including an electromagnet within the handlehousing.

FIG. 2 is a front view thereof.

FIG. 3 is a front view of a spring mechanism for a power deviceaccording to one embodiment.

FIG. 4 is a rear perspective view thereof;

FIG. 5 is a front perspective view thereof;

FIG. 6 is a side cross sectional view taken along line A-A in FIG. 3,showing the spring in a neutral position.

FIG. 6A is a perspective cross sectional view thereof.

FIG. 7 is a side cross sectional view taken along line A-A in FIG. 3,showing the spring in a more tensioned positioned.

FIG. 7A is a perspective cross sectional view thereof.

FIG. 8 is a perspective view of a spring mechanism with a workpiececonnected thereto, with the drive shaft and spring in a centralposition.

FIG. 9 is a rear view thereof.

FIG. 10 is a perspective view of a spring mechanism with a workpiececonnected thereto, with the drive shaft and spring in a left-rotatedposition.

FIG. 11 is a rear view thereof.

FIG. 12 is a perspective view of a spring mechanism with a workpiececonnected thereto, with the drive shaft and spring in a right-rotatedposition.

FIG. 13 is a rear view thereof.

FIG. 14 is a front view of a spring mechanism with a workpiece connectedthereto, with the drive shaft and spring in a central position.

FIG. 15 is a cross sectional view thereof taken along line C-C in FIG.14.

FIG. 16 is a front view of a spring mechanism with a workpiece connectedthereto, with the drive shaft and spring in a left-rotated position.

FIG. 17 is a cross sectional view thereof taken along line B-B in FIG.16.

FIG. 18 is a front view of a spring mechanism with a workpiece connectedthereto, with the drive shaft and spring in a right-rotated position.

FIG. 19 is a cross sectional view thereof taken along line D-D in FIG.18.

FIG. 20 is a side view of an electric toothbrush with a replacement headattached wherein the electromagnet and spring mechanism are visiblethrough the drive unit housing.

FIG. 21 is a front view according to a second embodiment of the presentinvention showing a spring mechanism as disposed within a handle housingshown in broken lines, and including an electromagnet within the handlehousing.

FIG. 22 is a side view thereof.

FIG. 23 is a perspective view of a spring mechanism for a power deviceaccording to the second embodiment.

FIG. 24 is a rear perspective view thereof.

FIG. 25 is another perspective view thereof.

FIG. 26 is a front view thereof.

FIG. 27 is a side cross sectional view along line E-E in FIG. 26.

FIG. 28 is a front view of a spring mechanism according to the secondembodiment with the drive shaft and spring in a central position.

FIG. 29 is a front view of a spring mechanism according to the secondembodiment with the drive shaft and spring in a right-rotated position.

FIG. 30 is a front view of a spring mechanism according to the secondembodiment with the drive shaft in a left-rotated position.

FIG. 31 is a bottom view of the spring mechanism of FIG. 28.

FIG. 32 is a bottom view of the spring mechanism of FIG. 29.

FIG. 33 is a bottom view of the spring mechanism of FIG. 30.

FIG. 34 is a cross sectional view taken along line A-A in FIG. 28.

FIG. 35 is a cross sectional view taken along line B-B in FIG. 29.

FIG. 36 is a cross sectional view taken along line C-C in FIG. 30.

DETAILED DESCRIPTION OF THE CURRENT EMBODIMENTS

I. Overview

A spring mechanism for use in powered devices such as an electrictoothbrush is shown in FIGS. 1-19 and generally designated 10. Thespring mechanism 10 includes: a fixed element 11 connected to a driveunit housing 12, a spring 14 connected to the fixed element 11, whereinat least a portion 16 of the spring 14 is movable with respect to thefixed element 11 and the housing 12, a drive shaft 18 that includes afirst end 20 having a magnet and a second end 24 for attachment to aworkpiece 26, and an adjustable tuning element 28 connecting the driveshaft 18 to the movable section 16 of the spring 14.

In operation, the spring mechanism 10 operates to convert or translatemovement of the magnet into a desired movement of the workpiece 26 at adesired frequency. The magnet is driven by a drive, such as anelectromagnet 30, positioned adjacent to the magnet. The adjustabletuning element 28 enables simple adjustment of the workpiece movementand frequency. In the illustrated embodiment, the workpiece 26 is areplacement head for an electric toothbrush and the spring mechanism 10provides the toothbrush head with a desired motion. In an alternativeembodiment, the spring mechanism 10 may form part of the replacementhead, rather than part of the drive unit housing.

II. Structure

As noted above, electromagnetic drive units are well known; therefore,the drive unit housing 12 and electromagnet 30 will not be described ingreat detail herein. Suffice it to say that the drive unit housing 12generally forms a handle for the drive unit and includes a power source(not shown) within the housing, such as a battery or AC power supply,and a switch 31 that is operable by the user. The drive unit housing 12includes a drive mechanism that may be a DC drive or an AC drive. In oneembodiment, the drive unit housing 12 includes an electromagnet 30positioned within the drive unit housing 12 that is actuated when theuser presses the switch 31. The electromagnet 30, or a pair ofelectromagnets, may be actuated to oscillate between positive andnegative polarities within the drive unit housing 12. The oscillationmay be over a range of resonant frequencies of the electromagnet. Asdepicted in FIGS. 1, 2 and 20, the electromagnet 30 is centrallypositioned within the drive unit housing 12 proximate the first end 20of the spring mechanism 10 drive shaft 18, and the spring mechanism 10is positioned within the housing 12. A portion of the drive shaft 18including the second end 24 of the drive shaft 18 extends outwardly froman end 34 of the housing 12 for receiving the workpiece 26.

The spring mechanism 10 may be designed for removably attaching to theworkpiece 26, such as a replacement toothbrush head or another type ofdevice intended for rotational oscillation. Referring to FIGS. 10-20, inone embodiment, the workpiece 26 is a toothbrush head that generallyincludes elongated neck 38 with a head 40 at one end, and a receptacle(not shown) at the opposite end. The receptacle is sized to receive thesecond end 24 of the drive shaft 18. As illustrated, the head 40includes a plurality of bristles 44 that may be of various lengthsextending outwardly from the head 40. In another embodiment, the head 40may include one or more alternative cleaning elements, such aselastomeric elements, extending from the head 40. In yet anotherembodiment, referenced above, the workpiece 26 may form a part of alarger replacement head that also includes the spring mechanism 10. Insuch an embodiment, the drive unit housing 12 may include structure,such as threads, for connecting to the replacement head and a portion ofthe spring mechanism 10 may extend into an opening in the drive unithousing 12 to enable the spring mechanism 10 to be driven by theelectromagnet 30.

Referring to FIGS. 1-20, the spring mechanism 10 includes the fixedelement 11, spring 14, drive shaft 18, and adjustable tuning element 28.In the illustrated embodiment, the fixed element 11 is connected to thelarger drive unit housing 12 by conventional means. The fixed element 11is connected to the drive unit housing 12 in such a way that the fixedelement 11 is fixed in place with respect to the drive unit housing 12.In one embodiment, the fixed element 11 is a generally flat, moldedplastic plate having an upper surface 46 and a lower surface 48. Thefixed element 11 may otherwise be formed from a variety of differentmaterials, and in one embodiment may be formed integrally with the driveunit housing 12. In the illustrated embodiment of FIGS. 1-7, the lowersurface 48 includes a pair of spaced-apart protrusions or bosses 50extending outwardly from the lower surface 48. The outer surfaces 52 ofthese bosses 50 may be concave in shape to form a portion of anengagement surface when engaged with a bearing member 80 on the driveshaft 18 described below. A second embodiment of the fixed element 11′is shown in FIGS. 10-19. In this variation (see FIG. 17), the fixedelement 11′ does not include outwardly extending bosses 50. Instead, apair of concave depressions 50′ in the lower surface 48′ of fixedelement 11′ form engagement surfaces 52′ that function similarly to theouter surfaces 52 on the bosses 50.

The spring member 14 is attached to the fixed element 11. In theillustrated embodiment, the spring member 14 is a generally flat plateformed of a resilient material such as spring steel. As illustrated, thespring 14 is attached to the fixed element 11 with four fasteners 56that extend through the fixed element 11 and the spring 14. Thefasteners 56 hold at least a portion of the spring 14 fixed with respectto the fixed element 11 and the drive unit housing 12. Of course, thespring 14 could be fixedly secured to the fixed housing 11 or the driveunit housing 12 in a variety of other conventional methods.

In one embodiment, the spring 14 further includes a movable section 16.As illustrated, the movable section 16 is a strip of the spring member14 that is formed between a pair of symmetric cutouts 60 in the spring14. In the illustrated embodiment, the movable section 16 is positionedcentrally within the spring 14, however, the movable section 16 mayotherwise be positioned at alternative locations on the spring asdesired depending on the application. By virtue of the cutouts 60, themovable section 16 is formed to include a first end 62 and a second end64 opposite the first end, such that the movable section 16 forms atorsion bar between the first 62 and second 64 ends that may twist backand forth along a spring axis defined along the longitudinal extent ofthe movable section 16 while the ends 62, 64 remain fixed. The size andshape of the cutouts 60 will control the degree of flexibility andtorsional rotation of the movable section 16 about the spring axis. Inthe illustrated embodiment, each cutout 60 is generally semi-circular,with the convex surfaces facing away from the movable section 16;however, the shape of the cutouts 60 may be changed in order to alterthe characteristics of the movable portion 16. In order to increaseflexibility in the movable section 16, and thus increase the movement ofthe drive shaft 18 and workpiece 26, the cutouts may be made larger, andthe movable section thinner. In one embodiment, the size and shape ofthe cutouts 60 and the movable section 16 are preselected by themanufacturer in accordance with the size and shape of the drive shaft 18and workpiece 26 in order to produce a desired workpiece motion, forexample, wherein the frequency of the electromagnetic drive mechanism 30approximates the resonant frequency of the workpiece 26. In oneembodiment, the movable section 16 defines a central opening 66 forreceiving the adjustable tuning element 28 as described in more detailbelow. Other characteristics of the spring may also be altered to changethe motion of the workpiece 26, for example, a thicker spring materialwill increase the force required to twist the spring and reduce theamount that the spring will twist during operation. Additional elementssuch as slots and holes may further be incorporated into the spring, ormultiple springs, to provide the spring(s) with desired characteristics.In one embodiment, the spring 14 may include holes that enable thebosses 50 on the fixed element to extend through the spring 14 and intoengagement with the drive shaft 18. Alternatively, the spring may beconfigured without these openings such that the spring forms engagementsurfaces for the drive shaft 18.

Although the movable section 16 of the spring 14 is illustrated as aportion of the larger spring member that is defined between a pair ofcutouts, it should be understood that in an alternative embodiment, thespring 14 may be comprised solely of a movable portion, such as agenerally flat strip of spring material that is fixed on opposite endsto form a torsion bar with characteristics similar to that of themovable section 16.

The drive shaft 18 is a generally elongated member defining alongitudinal axis 68, and having a first end 20 and a second end 24opposite the first end. The drive shaft 18 may be formed integrally as asingle unitary piece of material, but in the illustrated embodiment isformed from two materials and two pieces including a molded plasticmember 70 that includes the first end 20 of the drive shaft 18 and ametal member 71 that extends into a recess in the plastic member 70along the longitudinal axis and includes the second end 24 of the driveshaft 18. As illustrated, the first end 20 of the drive shaft 18includes a base 72, which is a generally flat plate extending outwardlyfrom the first end 20 of the drive shaft 18 in a direction generallyperpendicular to the longitudinal axis 68 of the drive shaft 18. Thebase 72 has a lower surface 74 that supports a pair of permanent magnets76, 78 of opposite polarities for instance, by molding the magnets intothe base 72, or with an adhesive or by other known means. Alternatively,the magnets 76, 78 may be indirectly connected to the base 72 by anintermediate plate, for example. As shown in FIGS. 1 and 2, whenassembled, the magnets 76, 78 are positioned adjacent to theelectromagnet 30. As a result of the magnets 76, 78 being positioned onthe base 72 such that they are offset from the longitudinal axis of thedrive shaft 18, the electromagnet will cause the magnets 76, 78 to movethe base 72 in an arcuate path. As illustrated, the base 72 includes anouter periphery that is smaller than the size of the interior of thedrive unit housing 12, so that the base 72 is capable of moving back andforth and/or up and down within the drive unit 12 housing. In oneembodiment, the magnets 76, 78 may be replaced by a ferromagneticmaterial, such as steel, that can be attracted to and repelled by theelectromagnet 30 within the drive unit housing 12.

The remainder of the plastic member 70 of the drive shaft 18 facilitatesengagement between the outer surfaces 52, 52′ on the fixed element 11 aswell as the connection between the drive shaft 18 and the movablesection 16 of the spring 14. Referring now to FIG. 15, the drive shaft18 includes a pair of rounded protrusions 80 forming rounded bearingsurfaces that engage the engagement surfaces 52, 52′ on the fixedelement 11 to determine a rocking-style relationship between the driveshaft 18 and the fixed element 11, wherein the rounded protrusions 80can rock back and forth on the concaved engagement surfaces 52. Inbetween the rounded protrusions 80, the drive shaft 18 includesstructure for connecting the drive shaft 18 to the movable section ofthe spring 16. In one embodiment, the drive shaft 18 defines a fastenerhole 82 extending therethrough for receiving the adjustable tuningelement 28 as described in more detail below. In another embodiment, analternative structure may be used to facilitate a rocking-style movementof the drive shaft 18 with respect to the fixed housing 11. For example,rounded protrusions may be included on the fixed housing 11 or springmember 14 to engage concave surfaces on the drive shaft 18, or the driveshaft 18 may be connected to the fixed housing with hinges. In eachcase, the connection of the drive shaft 18 to the fixed element 11causes the drive shaft 18 to move in an arcuate motion upon actuation ofthe electromagnet, the electromagnet 30 causing the permanent magnets76, 78 to move in an oscillating motion, and the connection of the driveshaft 18 to the fixed element 11 causing the drive shaft to move in anarcuate path about an axis that is parallel with the spring axis and thelongitudinal axis 68 of the drive shaft 18 along an axis generallyextending through the bearing surfaces.

Finally, the second end 24 of the drive shaft 18 is shaped to attach tothe workpiece 26. In the illustrated embodiment, the second end 24includes a shape that is formed to extend into the receptacle in theworkpiece 26 and prevent rotation or axial displacement of the workpiece26 with respect to the drive shaft 18. Referring now to FIGS. 1 and 2,the second end 24 extends outwardly beyond an end of the drive unithousing 12 for attachment to the work piece 26.

The adjustable tuning element 28 connects the drive shaft 18 to thespring 14. More particularly, the adjustable tuning element 28 connectsthe drive shaft 18 to the movable portion 16 of the spring 14. In theillustrated embodiment, the adjustable tuning element 28 is a threadedbolt that extends through the central opening 66 in the movable section16 of the spring 14, through the fastener hole 82 in the drive shaft 18,and into a tuning nut 84 on the rear surface of the drive shaft 18. Whenthe bolt 28 is inserted into the nut 84, the drive shaft 18 is connectedto the spring 14 and to the fixed element 11 with the engagementsurfaces 52 and 80 in engagement with one another to form bearings forthe rocking movement of the drive shaft 18. As a result of the threadson the bolt 28, the bolt 28 and nut 84 can be tightened or loosened toadjust the amount of tension placed on the movable section 16 of thespring 14. For example, FIG. 6 shows the tuning element 28 connected tothe nut 84 with the movable section 16 of the spring in a generallyneutral position aligned with the remainder of the flat spring 14. Inthis state, there may be a gap between the movable section 16 of thespring 14 and the drive shaft 18. FIG. 7 shows the tuning element 28connected more tightly onto the nut 84 with the movable section 16 ofthe spring 14 in a tensioned position wherein the movable section isflexed slightly toward the drive shaft 18, which may partially orcompletely close the gap between the drive shaft 18 and the spring 14.Variations in the amount of tension on the movable section 16 of thespring 14 will alter the amplitude and frequency of the movement of thedrive shaft 18 and the workpiece 26. As such, the manufacturer canefficiently tune the movement of the workpiece 26 by rotating the bolt28 with respect to the nut 84, therefore drawing the movable section 16toward the drive shaft 18 and adjusting the tension on the movablesection 16 of the spring 14. Alternate fasteners or devices that providea degree of adjustment may be substituted for the bolt style fastener invariations on the current design.

Notably, although the above disclosed embodiments are shown inconnection with toothbrush heads, they may also be used in connectionwith other types of workpieces that utilize the same or similar rangesof motion, such a cleaning brush and/or an exfoliating brush withbristles arranged generally parallel to the longitudinal length of thedrive shaft 18.

III. Operation

During operation, the electromagnet 30 within the drive unit housing 12is operated by the user manipulating switch 31. When actuated, theelectromagnet 30 may oscillate and/or be controlled to change polaritiesover a range of drive frequencies. The replacement head or otherworkpiece 26 is connected to the end 24 of the drive shaft 18 byinserting the second end 24 of the drive shaft 18 into the receptacle onthe workpiece 26—or by another attachment method. The electromagnet 30,and its attraction to the permanent magnets 76, 78 (or ferromagneticmaterial) on the base 72 causes the base 72 to oscillate back and forthin an arcuate path.

The spring mechanism 10 controls the path of movement of the drive shaft18, as well as the amplitude and frequency of movement of the workpiece26. Referring to spring mechanism 10, the movement of the base 72 causesthe drive shaft 18 to rotate back and forth about a rotation axisextending through the bearing surface 80—specifically the engagementsurface between the bearing surface 80 and the surfaces 52, 52′ of thefixed housing 11 because of the connection between the drive shaft 18and the movable portion 16 of the spring 14. The rotation axis isgeneral parallel to the spring axis and the longitudinal axis 68 of thedrive shaft 18. The movable section 16 of the spring 14 rotates aboutthe spring axis as the drive shaft 18 oscillates, and acts to controlthe movement of the drive shaft 18 and bias the drive shaft 18 in acentral position. As the spring 74 twists, the workpiece 26 moves in anarcuate path.

The motion of the spring mechanism 10 and workpiece 26 is depicted indetail in FIGS. 8-19. FIGS. 8-9 and 14-15 show the spring mechanism 10in a central position, which may be a neutral resting position when theelectromagnet is off, and may be a central position of rotation when theelectromagnet is actuated. In this position, the movable portion 16 ofthe spring 14 lies generally in the same plane as the remainder of thespring 14 in a non-twisted state. As shown in FIG. 15, the bearingsurface 80 on the drive shaft engages the surface 52′ of the fixedhousing 11 (extending through an opening defined in the spring 14) andthe bristles 44 on the workpiece 26 are generally perpendicular to theupper surface 46 of the fixed element 11. FIGS. 10-11 and 16-17 show thespring mechanism 10 in a left-rotated position, occurring when theelectromagnet is actuated. In this position, the movable portion 16 ofthe spring 14 lies generally in a plane that is angled with respect tothe remainder of the spring 14 in a twisted state. As shown in FIG. 17,the bearing surface 80 on the drive shaft engages the surface 52′ of thefixed housing 11 (extending through an opening defined in the spring 14)and the bristles 44 on the workpiece 26 are generally rotated to theleft with respect to the upper surface 46 of the fixed element 11.Finally, FIGS. 12-13 and 18-19 show the spring mechanism 10 in aright-rotated position, occurring when the electromagnet is actuated. Inthis position, the movable portion 16 of the spring 14 lies generally ina plane that is angled to the right with respect to the remainder of thespring 14 in a twisted state. As shown in FIG. 19, the bearing surface80 on the drive shaft engages the surface 52′ of the fixed housing 11(extending through an opening defined in the spring 14) and the bristles44 on the workpiece 26 are generally rotated to the right with respectto the upper surface 46 of the fixed element 11. For the duration thatthe electromagnet 30 is actuated, the spring mechanism 10 oscillatesback and forth between the left-rotated and right-rotated positions.

As noted above, the motion and frequency of the workpiece, such as thebristle head 40 or the workpiece of another type of device, may becontrolled by a variety of variables. In the present invention, this mayinclude adjustment of the adjustable tuning element 28. Other variablesinclude, but are not limited to, the size, thickness and shape of thespring, the positioning of the magnets on the bottom member, the sizeand length of the bristles, and the drive frequency of the motor. Eachof these variables can be adjusted from application to application toprovide a desirable user experience in terms of brushing function,handle vibration and operating noise. In one embodiment, the drivefrequency of the motor is between about 60 Hz and 1000 Hz. In a moreparticular embodiment for use with an electric toothbrush, the drivefrequency is between about 150 Hz and 400 Hz. In a more particularembodiment for an electric toothbrush, the drive frequency of the motoris between about 230 Hz and 280 Hz, and in an even more particularembodiment for an electric toothbrush the drive frequency of the motoris set to about 260 Hz. In an embodiment wherein the workpiece is thehead of an exfoliator, the drive frequency may be between about 150 and200 Hz. The drive frequency for alternative workpiece applications, suchas those listed above, may be increased or decreased depending on thedesired power and workpiece motion for the particular application.

After a particular drive frequency is determined, the above notedvariables are adjusted to achieve the desired motion and frequency ofthe bristle head 40 while maintaining a relatively low sound level and arelatively low current draw on the motor. In one embodiment for use withan electric toothbrush, the desired frequency of the bristle head isbetween about 245 Hz and 255 Hz. In another embodiment, the desiredrange of motion of the tips of the bristles is between about 0.370 mmand 0.575 mm. In yet another embodiment, the desired sound level of theoperating toothbrush containing one of the above noted embodiments isbelow about 73 dB, and more particularly, below about 60 dB. If, afterassembly and after an initial testing operation, the workpiece movementis found to be incorrect, a manufacturer may simply adjust the tuningelement 28 to achieve the desired motion.

IV. Second Embodiment

A second embodiment of a spring mechanism for use in powered devicessuch as an electric toothbrush is shown in FIGS. 21-36 and generallydesignated 100. The spring mechanism 100 is similar to the springmechanism 10 in that it includes: a spring 114 connected to a drive unithousing 112. In this embodiment, at least two portions 116, 117 of thespring 114 are movable with respect to the housing 112. The drive shaft118 includes a first end 120 having a magnet and a second end 124 forattachment to a workpiece (such as the workpiece 26 shown in connectionwith the spring mechanism 10), and at least two adjustable tuningelements 128, 129 connect the drive shaft 118 to the movable sections116, 117 of the spring 114.

In operation, the spring mechanism 100 operates similar to the springmechanism 10 to convert or translate movement of the magnet into adesired movement of the workpiece at a desired frequency. The magnet isdriven by a drive, such as an electromagnet 130, positioned adjacent tothe magnet on the drive shaft 118. In this embodiment, the multipleadjustable tuning elements 128, 129 enable a high degree of adjustmentof the workpiece movement and frequency.

The electromagnetic drive unit of the second embodiment 100 issubstantially the same as that of the first embodiment 10. The housing112 includes an electromagnet or a pair of electromagnets 130 and aswitch 131 that is operable by the user. A portion of the drive shaft118 including the second end 124 of the drive shaft 118 extendsoutwardly from an end 134 of the housing 112 for receiving theworkpiece. The workpiece of the second embodiment may be a variety ofworkpieces including any of the variety of workpieces 26 describedabove.

Referring to FIGS. 21-36, the spring mechanism 100 includes a spring114, drive shaft 118, and adjustable tuning elements 128, 129. In thisembodiment, the spring 114 is connected to the larger drive unit housing112 by conventional means. In one embodiment, the spring may beconnected to a fixed element such as the fixed element 11 describedabove. The spring may alternatively be attached to the housing 112 byanother method such as fasteners that extend through the spring 114. Inthe illustrated embodiment, the spring member 114 is a generally flatplate formed of a resilient material such as spring steel. At least aportion of the spring 114 is fixed with respect to the drive unithousing 112.

The spring 114 includes multiple movable sections, and in the embodimentillustrated in FIGS. 21-36, the spring 114 includes a pair of movablesections 116, 117. Each movable section 116, 117 may be a strip of thespring member 114 that is formed between a pair of symmetric cutouts 160in the spring 114. As shown, each movable section 116, 117 is positionedcentrally within the spring 114 such that they are aligned with eachother along a longitudinal axis of the movable sections 116, 117 of thespring 114, however, the movable sections 116, 117 may otherwise bepositioned at alternative locations on the spring as desired dependingon the application. For example, staggering the movable sections 116,117 on opposite sides of the longitudinal centerline of the spring 114may provide an alternative but desirable workpiece motion.

By virtue of the cutouts 160, each movable section 116, 117 is formed toinclude a first end 162 and a second end 164 opposite the first end,such that the movable sections 116, 117 each form a torsion bar betweenthe first 162 and second 164 ends that may twist back and forth along aspring axis defined along the longitudinal extent of the movable section116, 117 while the ends 162, 164 remain fixed. The size and shape of thecutouts 160 will control the degree of flexibility and torsionalrotation of the movable sections 116, 117 about the spring axis. In theillustrated embodiment, each cutout 160 for each of the movable sections116, 117 is generally semi-circular, with the convex surfaces facingaway from the movable sections 116, 117; however, the shape of thecutouts 160 may be changed in order to alter the characteristics of themovable portion 116. In order to increase flexibility in the movablesection 116, and thus increase the movement of the drive shaft 118 andworkpiece, one or more of the cutouts may be made larger, and themovable sections thinner. In one embodiment, the size and shape of thecutouts 160 and the movable sections 116, 117 are preselected by themanufacturer in accordance with the size and shape of the drive shaft118 and workpiece in order to produce a desired workpiece motion, forexample, wherein the frequency of the electromagnetic drive mechanism130 approximates the resonant frequency of the workpiece. The size andshapes of the cutouts 160 of one of the movable sections 116 may also bevaried with respect to the size and shape of the cutouts 160 of theother movable section 117 to further refine the characteristics of thedriveshaft 118 and workpiece movements. For example, if the movablesection 116 is constructed to provide a greater degree of flexibilitythan the movable section 117, then the workpiece may have greateramplitude of movement.

In one embodiment, each movable section 116, 117 defines a centralopening 166 for receiving the respective adjustable tuning element 128,129 in a manner similar to that described above. As noted above, othercharacteristics of the spring may also be altered to change the motionof the workpiece, for example, a thicker spring material will increasethe force required to twist the spring and reduce the amount that thespring will twist during operation. Additional elements such as slotsand holes may further be incorporated into the spring, or multiplesprings, to provide the spring(s) with desired characteristics.

Although the movable sections 116, 117 of the spring 114 are illustratedas a portion of the larger spring member 114 that is defined between apair of cutouts, it should be understood that in an alternativeembodiment, the spring 114 may be comprised solely of a movable portion,such as a generally flat strip of spring material that is fixed onopposite ends to form a torsion bar with characteristics similar to thatof the movable sections 116, 117.

The drive shaft 118 is a generally elongated member defining alongitudinal axis 168, and having a first end 120 and a second end 124opposite the first end. The drive shaft 118 of the illustratedembodiment is constructed similar to the drive shaft 18 in that it isformed from two materials and two pieces including a molded plasticmember 170 that includes the first end 120 of the drive shaft 118 and ametal member 171 that extends into a recess in the plastic member 170along the longitudinal axis and includes the second end 124 of the driveshaft 118. As illustrated, the first end 120 of the drive shaft 118includes a base 172, which is a generally flat plate extending outwardlyfrom the first end 120 of the drive shaft 18 in a direction generallyperpendicular to the longitudinal axis 168 of the drive shaft 118. Thebase 172 has a lower surface 174 that supports a pair of permanentmagnets 176, 178 of opposite polarities for instance, by molding themagnets into the base 172, or with an adhesive or by other known means.Alternatively, the magnets 176, 178 may be indirectly connected to thebase 172 by an intermediate plate, for example. As shown in FIGS. 21 and22, when assembled, the magnets 176, 178 are positioned adjacent to theelectromagnet 130. As a result of the magnets 176, 178 being positionedon the base 172 such that they are offset from the longitudinal axis ofthe drive shaft 118, the electromagnet will cause the magnets 176, 178to move the base 172 in an arcuate path. As illustrated, the base 172includes an outer periphery that is smaller than the size of theinterior of the drive unit housing 112, so that the base 172 is capableof moving back and forth and/or up and down within the drive unit 12housing. In one embodiment, the magnets 176, 178 may be replaced by aferromagnetic material, such as steel, that can be attracted to andrepelled by the electromagnet 130 within the drive unit housing 112.

The remainder of the plastic member 170 of the drive shaft 118facilitates engagement with the movable sections 116, 117 of the spring114 (or in another embodiment, with a portion of a fixed elementattached to the spring 118). Referring now to FIG. 27, the drive shaft118 includes structure for connecting the drive shaft 118 to the movablesections 116, 117 of the spring 114. In one embodiment, the drive shaft118 defines a pair of fastener holes 182, 183 extending therethrough forreceiving the adjustable tuning elements 128, 129 as described in moredetail below. As shown, each fastener hole 182, 183 may be definedwithin an upstanding boss 190, 191 that protrudes from the drive shaft118. These bosses 190, 191 contact the spring 114 within the movableportions and adjacent to the adjustable tuning elements 128, 129providing a pivot point about when the movable sections 116, 117 canrotate. In another embodiment, an alternative structure may be used tofacilitate a rocking-style movement of the drive shaft 118 with respectto the housing 112, such as the rounded protrusions described inconnection with the spring element 10 above. In each case, theconnection of the drive shaft 118 to the movable sections of the spring114 causes the drive shaft 118 to move in an arcuate motion uponactuation of the electromagnet, the electromagnet 130 causing thepermanent magnets 176, 178 to move in an oscillating motion about thelongitudinal axes of the movable sections 116, 117. Finally, the secondend 124 of the drive shaft 118 is shaped to attach to a workpiece in thesame manner as described above in connection with workpiece 26.

The adjustable tuning elements 128, 129 connect the drive shaft 118 tothe spring 114. More particularly, the adjustable tuning elements 128,129 connect the drive shaft 118 to the movable portions 116, 117 of thespring 114. In the illustrated embodiment, the adjustable tuningelements 128, 129 are threaded bolts that extend through the centralopenings 166 in the movable sections 116, 117 of the spring 114, throughthe fastener holes 182, 183 in the drive shaft 118, and into respectivetuning nuts 84 on the rear surface of the drive shaft 118. When thebolts 128, 129 are inserted into the nuts 84, the drive shaft 118 isconnected to the spring 114 with the engagement of the bosses 190, 191with the spring 114 within the movable sections 116, 117. As a result ofthe threads on the bolts 128, 129, they can be tightened or loosened toadjust the amount of tension placed on each of the movable sections 116,117 of the spring 114 in a manner similar to that described above andillustrated in FIGS. 6 and 7. Variations in the amount of tension on oneor both of the movable sections 116, 117 of the spring 114 will alterthe amplitude and frequency of the movement of the drive shaft 118 andthe workpiece. As such, the manufacturer can efficiently tune themovement of the workpiece by rotating one or both of the bolts 128, 129with respect to the nuts 84, therefore drawing the movable sections 116,117 toward the drive shaft 118 and adjusting the tension on the movablesections 116, 117 of the spring 114. Alternate fasteners or devices thatprovide a degree of adjustment may be substituted for the bolt stylefastener in variations on the current design.

Although the above disclosed embodiments are shown in connection withtoothbrush heads, they may also be used in connection with other typesof workpieces that utilize the same or similar ranges of motion, such acleaning brush and/or an exfoliating brush with bristles arrangedgenerally parallel to the longitudinal length of the drive shaft 18,118.

During operation, the electromagnet 130 within the drive unit housing112 is operated by the user manipulating switch 131 in a manner similarto that described above in connection with spring mechanism 10. Thespring mechanism 100 controls the path of movement of the drive shaft118, as well as the amplitude and frequency of movement of theworkpiece. Referring to spring mechanism 100, the movement of the base172 causes the drive shaft 118 to rotate back and forth about a rotationaxis extending generally along the spring axis defined by the movableportions 116, 117 of the spring 114 to the extent that the movableportions 116, 117 are aligned as they are in the illustrated embodiment.The rotation axis is general parallel to the spring axis and thelongitudinal axis 168 of the drive shaft 118. The movable sections 116,117 of the spring 114 rotate about the spring axis as the drive shaft118 oscillates, and act to control the movement of the drive shaft 118and bias the drive shaft 118 in a central position. As the movablesections 116, 117 twist, the workpiece moves in an arcuate path.

The motion of the spring mechanism 100 is depicted in detail in FIGS.28-36. FIGS. 28, 31 and 34 show the spring mechanism 100 in a centralposition, which may be a neutral resting position when the electromagnetis off, and may be a central position of rotation when the electromagnetis actuated. In this position, the movable portions 116, 117 of thespring 114 lie generally in the same plane as the remainder of thespring 114 in a non-twisted state. As shown in FIG. 34, the boss 190 onthe drive shaft 118 engages the spring 114 within the movable portion116. FIGS. 30, 33 and 36 show the spring mechanism 100 in a left-rotatedposition, occurring when the electromagnet is actuated. In thisposition, the movable portions 116, 117 of the spring 114 lie generallyin a plane that is angled with respect to the remainder of the spring114 in a twisted state. Finally, FIGS. 29, 32 and 35 show the springmechanism 100 in a right-rotated position, occurring when theelectromagnet is actuated. In this position, the movable portion 116 ofthe spring 114 lies generally in a plane that is angled to the rightwith respect to the remainder of the spring 114 in a twisted state. Forthe duration that the electromagnet 130 is actuated, the springmechanism 100 oscillates back and forth between the left-rotated andright-rotated positions.

As noted above and in connection with the spring mechanism 100, themotion and frequency of the workpiece may be controlled by a variety ofvariables. In the present invention, this may include adjustment of oneor both of the adjustable tuning elements 128, 129. Other variablesinclude, but are not limited to, the size, thickness and shape of thespring, the positioning of the magnets on the bottom member, the sizeand length of the bristles or other elements extending from theworkpiece, and the drive frequency of the motor. Each of these variablescan be adjusted from application to application to provide a desirableuser experience in terms of brushing function, handle vibration andoperating noise. The drive frequency of the motor, and the relativefrequencies of the motor and the workpiece, may be determined as notedabove in connection with spring mechanism 10. The spring mechanism 100provides a broad range of adjustability due to the ability to adjust thecharacteristics of one or both of the tuning elements 128, 129 andmovable spring sections 116, 117. As noted above, manufacturers may varythe characteristics of both tuning elements 128, 129 and both movablespring sections 116, 117 uniformly, or they may adjust thecharacteristics of one tuning element and/or one spring section withrespect to the other.

The above description is that of the current embodiment of theinvention. Various alterations and changes can be made without departingfrom the spirit and broader aspects of the invention as defined in theappended claims, which are to be interpreted in accordance with theprinciples of patent law including the doctrine of equivalents. Anyreference to claim elements in the singular, for example, using thearticles “a,” “an,” “the” or “said,” is not to be construed as limitingthe element to the singular.

The invention claimed is:
 1. A spring mechanism for a power device, thedevice including an electromagnet, the spring mechanism comprising: ahousing; a spring connected to the housing, wherein at least twoportions of said spring are movable with respect to said housing, andsaid movable portions of said spring are torsion bars each formedbetween a pair of symmetric cutouts defined in said spring; a driveshaft that includes a first end having a magnet and a second end forattachment to a workpiece; and adjustable tuning elements connectingsaid drive shaft to each of the torsion bars of said spring such thatthe spring twists back and forth along a spring axis defined alonglongitudinal extents of the torsion bars.
 2. The spring mechanism ofclaim 1 wherein said longitudinal extents of the torsion bars being inalignment with one another.
 3. The spring mechanism of claim 2 whereinsaid spring is a flat spring, and said movable portions are formedbetween said cutouts such that said movable portions are surroundedwithin said flat spring.
 4. The spring mechanism of claim 3 wherein saidadjustable tuning elements extend from said drive shaft to said movableportions of said spring, said adjustable tuning elements connected tosaid spring such that each said adjustable tuning element places saidmovable portion of said spring under a degree of tension, saidadjustable tuning elements being independently tunable such that thedegree of tension on one said movable portion of said spring is at leastone of the same and different from another said movable portion of saidspring.
 5. The spring mechanism of claim 4 wherein said adjustabletuning elements are each threadedly connected between said drive shaftand said movable portions of said spring, said threaded connectionenabling said independent adjustment of the amount of said tension oneach said movable portion of said spring.
 6. The spring mechanism ofclaim 5 wherein said adjustable tuning elements extend generallyperpendicular to a rotation axis of the shaft, and wherein saidadjustable tuning elements are generally in alignment along alongitudinal axis of the spring mechanism.
 7. The spring mechanism ofclaim 6 wherein said adjustable tuning elements are spaced apart alongsaid longitudinal axis of said spring mechanism.
 8. The spring mechanismof claim 7 wherein a pair of bosses extend outwardly from said driveshaft, each said boss aligned with one of said movable portions of saidspring.
 9. The spring mechanism of claim 8 wherein each said bossextends into engagement with one of said movable portions of saidspring, each said boss defining an opening, wherein one of saidadjustable tuning elements extends into each said opening.
 10. A springmechanism for a power device, the device including an electromagnet, thespring mechanism comprising: an elongated drive shaft having a first endand a second end opposite said first end for attaching to a workpiece,said drive shaft defining a longitudinal axis, said first end includinga base extending outwardly from said longitudinal axis, said baseincluding a magnet proximate the electromagnet; a fixed housingincluding a spring member, said spring member having at least twomovable sections capable of torsional rotation about a spring axis, saidspring axis generally parallel to said longitudinal axis of said driveshaft, said movable sections of the spring member are torsion bars eachformed between a pair of symmetric cutouts defined in said spring memberand aligned along said longitudinal axis with said torsion barspositioned adjacent said drive shaft between said first end and saidsecond end of said drive shaft; at least two tuning members, each saidtuning member extending between said drive shaft and an associated oneof said movable sections of said spring member such that the springmember twists back and forth along longitudinal extents of the torsionbars.
 11. The spring mechanism of claim 10 wherein said spring member isa flat spring and said movable sections are spaced apart from oneanother and said movable portions are formed between said cutouts suchthat said movable portions are surrounded within said flat spring. 12.The spring mechanism of claim 10 wherein said tuning members areindependently adjustable to adjust a degree of tension on said movablesections of said spring in a direction generally perpendicular to saidspring axis.
 13. The spring mechanism of claim 12 wherein said each ofsaid tuning members is a threaded member extending through said movablesection of said spring and through said drive shaft.
 14. The springmechanism of claim 10 wherein said drive shaft includes at least oneupwardly extending boss aligned with one of said movable sections ofsaid spring member.
 15. The spring mechanism of claim 14 wherein said atleast one boss extends from said drive shaft into engagement with saidone of said movable sections of said spring member.
 16. The springmechanism of claim 15 wherein said drive shaft includes at least two ofsaid bosses, each said boss defining an opening, said tuning elementseach extending into one of said openings.
 17. The spring mechanism ofclaim 10 wherein said base at said first end of said drive shaft extendstowards said spring member.
 18. A method of manufacturing a springmechanism for an electric toothbrush, comprising: providing a fixedhousing defining a generally hollow interior; providing a drive shaftextending at least in part into the hollow interior of the fixedhousing, the drive shaft having a first end and a second end, the firstend including a magnet and the second end adapted to receive aworkpiece; connecting a spring member to the fixed housing, the springmember having at least two movable sections spaced apart from oneanother and defined as torsion bars formed between a pair of symmetriccutouts in the spring member; connecting the spring member to the driveshaft with at least two tuning members such that the spring memberextends adjacent to the drive shaft with the movable sections positionedbetween the first end and the second end of the drive shaft and thespring member twists back and forth along a spring axis defined alonglongitudinal extents of the torsion bars; and adjusting at least one ofthe tuning members to provide a desired degree of tension on one of themovable sections of the spring.
 19. The method of claim 18 wherein theadjusting of the tuning member includes drawing the one of the movablesections of the spring member towards the drive shaft.
 20. The method ofclaim 19 wherein the spring is a flat spring and the tuning members eachextend through an associated one of the movable sections of the springand into the drive shaft.